Electret Incorporated AlN Substrates for Partial Discharge Mitigation in 3.3 Kv Power Module Operating at High Temperature

Electrets exhibit a quasi-permanent electric charge or polarization, setting them apart from typical dielectric materials. They can neutralize high electric fields concentrated at critical points such as triple points, bubbles, and air gaps. Previous research has shown that electrets can effectively mitigate partial discharge (PD) under steep voltage pulses by countering concentrated electric fields, thereby preventing PD in various scenarios. In this study, we aim to reduce PD in 3.3 kV devices using thin-film Parylene HT coatings. Aluminum nitride (AIN) substrates are coated with squared-ring-shaped thin film, Parylene HT, and PD magnitude is measured. The experiment examines PD behavior at two temperatures- 25° C and 180° C. High <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$d v/d t$</tex> square pulse voltages, with a slew rate of up to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$165 ~\mathrm{V}/\text{ns}$</tex>, are applied. Results indicate that Parylene HT coatings can significantly reduce PD magnitude, even under extreme thermal conditions. Furthermore, this research lays the groundwork for the future incorporation of electrets into power substrates, which will play a crucial role in high-voltage power modules, enhancing their insulation performance and reliability in harsh operating environments.